Some hand grips gripped by riders of, e.g., motorcycles have a built-in heater for warming up his or her gripping hands. Among such hand grips, some known ones are provided with a temperature sensor for controlling the quantity of heat generated by the heater. Specifically, in a known hand grip, a thermistor is bonded, with an adhesive of epoxy resin, to the surface of a flexible circuit provided with a heating resistive wire and wound around a grip sleeve (see, e.g., Patent Document 1). Such a flexible circuit and thermistor are covered with, e.g., a synthetic rubber molded part.